Ok, so I've been doing a little research on this. My dog is a 4 year old male neutered Bichon.

He was fine with house training until we got another Bichon 9 months ago. They two absolutely love one another. The only problem is that Monty, the four year old has been marking territory EVERYWHERE since we got Wilbur.

He lifts his leg on everything. By everything I mean anything to a throw rug, clothes on the floor, to upright objects such as our refrigerator. There is dog urine everywhere in my home and its becoming frustrating to keep up with. He has even attempted to lift his leg on me. I will put him outside for a half hour and as soon as he comes in he lifts his leg on something. He has been to the vet, and there is nothing medically wrong with him. There are even times when he lifts his leg and no pee comes out at all. These dogs are like our children so I could never dream of giving either of them away. I need help please, any advice would be greatly appreciated

Welcome to the forum, we would love to see pics if you have some to share.

Is the new pup neutered?

What are you cleaning the urine spots with? An enzymatic cleaner like Nature's Miracle will eliminate the odour at the cellular level by breaking up & removing the odour you can't smell but they can. You can also make your own enzyme cleaner with 1 cup water + 1/4 isopropyl (rubbing) alcohol + 1/4 cup vinegar, spray the area, blot up w/clean rag/paper towel, re-spray & let dry

I'll leave the re-training advice to those with more experience than I with these types of situations.

__________________
Avoid biting when a simple growl will do

The Spirit Lives As Long As Someone Who Lives Remembers You - Navaho Saying

Vindication ~ For all those pets who became sick or lost their lives from tainted pet food

Belly band him! Search on Etsy for them, they're cloth with velcro and they go around the dog's 'stuff' so if he pee's he's sitting in a soaked belly band. Try using that for a month then take it off and see if the behaviour continues.

Are both of your dogs male, and are they neutered? My boyfriends mom has this problem with her two Italian Greyhounds and I think it has to do with establishing who is boss in the house. I'm not sure how to advise you to stop it, but I think that's what's going on.